Centrifugal compressor



July 11, 1967 w. J. LEE 3,330,473

CENTRIFUGAL COMPRESSOR Filed March 29, 1965 I 2 Sheets-Sheet 1 F/GZ/ l11 I I [fliTlll I MLF/PE'D J.

July 11, 1967 w. J. LEE 3,330,473

CENTRIFUGAL COMPRESSOR Filed March 29, 1965 2 Sheets-Sheet 2 INVENTOR.W/LFRED J L 55 ATTORNEYS United States Patent 3,330,473 CENTRIFUGALCOMPRESSOR Wilfred J. Lee, East Syracuse, N.Y., assignor to BelsonCorporation, New York, NY. Filed Mar. 29, 1965, Ser. No. 443,335 Claims.(Cl. 230-115) The present invention relates to centrifugal machines suchas compressors and exhausters and more particularly to an anti-surgingcontrol device for such machines.

It is Well known in the art of centrifugal compressors and exhaustersthat under certain operating conditions of the machine the medium beinghandled will surge or pulsate violently in the compressor system. Suchsurging occurs under different operating conditions for differentmachines in accordance with their particular design. In general,however, surging occurs at a high outlet pressure and low inlet volume.As the machine is doing a minimum amount of work under these conditions,the power required to operate the machine and the rate of flow throughboth the inlet and outlet is at a minimum.

Such surging is undesirable, and devices have heretofore been providedto prevent surging. Such prior antisurging devices usually comprise athrottling valve in the inlet to the machine to restrict flow theretoand thereby maintain stable operation. For example, the throttling valvemay be operated by the pressure produced at the outlet of the compressorto move the valve to some equilibrium position Where the flow to themachine is restricted sufliciently to prevent sudden surging of themedium being handled. As a result, the compressor operates at reducedefficiency because of the continuous throttling effect produced by theanti-surge valve at all operating flow rates. This reduced efficiencyand pressure drop across the throttling valve of such anti-surgingcontrol devices, therefore, will occur below as well as above thecritical operating conditions at which surging is apt to start.

One of the objects of the present invention is to provide ananti-surging control device for a centrifugal machine which permitsoperation of the machine at maximum efiiciency until it approaches acritical condition at which surging may occur.

Another object is to provide an anti-surging control device of the typeindicated which is brought into operation automatically in response toan operating condition of the compressor which may produce surging.

Another object is to provide an anti-surging control device of the typeindicated which is adapted for use when the machine operates as anexhauster as well as when it operates as a compressor.

Still another object is to provide an anti-surging control device of thetype indicated which is of relatively simple and compact construction,economical to manufacture and one which is reliable in operation inperforming its intended function.

These and other objects will become more apparent from the followingdescription and drawings in which like reference characters denote likeparts throughout the several views. It is to be expressly understood,however, that the drawings are for the purpose of illustration only andare not a definition of the limits of the invention, reference being hadfor this purpose to the appended claims.

In the drawings:

FIGURE 1 is a side elevational view of an electric motor drivencentrifugal compressor incorporating the novel anti-surging controldevice of the present invention and showing the current responsive relayfor bringing the device into and out of operation;

FIGURE 2 is an enlarged view of the anti-surging con- I 3,330,473Patented July 11, 1967 trol device, partly in section, and showing therelationship of the parts during stable operating conditions;

FIGURE 3 is a view similar to FIGURE 2 showing the relationship of theparts to throttle flow through the machine under operating conditionswhen surging is apt to occur.

FIGURE 4 is a sectional plan view taken on line 44 of FIGURE 3 to showthe butterfly throttling valve in detail; and

FIGURE 5 is a view similar to FIGURE 1 showing the anti-surging controldevice applied to an exhauster and the flow operated vane type switchfor starting and stopping its operation.

In the drawings, FIGURE 1 illustrates a centrifugal machine 6 to whichthe anti-surging control device 7 of the present invention is shownapplied. In the illustrated embodiment, the centrifugal machine is of aconventional design and operating as a compressor having an inlet 8 andan outlet 9. The inlet 8 and outlet 9 comprise ports in the casing andpipes connected thereto and for purposes of description these elementswill be referred to generally as the inlet and outlet. The centrifugalcompressor 6 is driven by an electric motor 10 to which the current issupplied through the power lines P-1, P-2 and P-3.

The anti-surging control device of the present invention is illustratedin FIGURES 1 to 5 of the drawings as comprising a butterfly valve 11having separate vanes 12 and 13 pivotally mounted for rocking movementon a common axis across the inlet 8. As shown most clearly in FIGURE 4the vanes 12 and 13 are of generally hemispherical shape and each hassleeve sections 15 and 16, respectively, which interleave with eachother on a shaft 17 to form a piano hinge. One end 17a of the shaft 17and the sleeve section 15 at the opposite end of the shaft are journaledin bearings 18 and 19 at opposite sides of the inlet 8. The sleevesections 16 and 16a of the vane 13 are rigidly attached to shaft 17 bymeans of pins 20 and 21 for rotation therewith and sleeve sections 15and 15a of vane 12 rotate on the shaft. Ends 17b of the shaft 17connected to vane 13 and 15b of the sleeve section 15 on the vane 12extend through and beyond the bearing 19 for different distances andhave radially extending arms 25 and 26 thereon. Operating arm 25 has ahub 27 clamped to the extended end 15b of the sleeve and arm extendsradially from the sleeve at the opposite side of the shaft from its vane12. Arm 2.6 also has a hub 28 clamped to the extended end 17b of theshaft 17 at the opposite side of the shaft from its vane 13. Sleevesection 15a of the vane 12 remote from the bearing 19 has a rollerbearing 29 surrounding the shaft 17 to support the free end of the vane.Thus, rocking movement of the arms 25 and 26 downwardly from theposition illustrated in FIGURE 2 to that illustrated in FIGURE 3actuates the vanes 12 and 13 from a parallel back to back relationshipatthe center of the inlet 8 Where they present a minimum resistance toflow to an extended relationship across the inlet to resist flow. I

The vanes 12 and 13 are operated simultaneously by a fluid motor 30having a cylinder 31 and piston 32 therein. A piston rod 33 extendingthrough one end of the cylinder 31 is connected to a cross head 34.Cross head 34 is in the form of a yoke having depending legs 35 and 36and the lower ends of the legs are connected to the outer ends of theoperating arms 25 and 26 and the vanes 12 and 13 by adjustable links 37and 38. Thus, when fluid pressure is supplied to the top of the piston32 as viewed in FIGURE 2, it moves the piston rod 33 and cross head 34downwardly and acting through the links 37, 38 and arms 25, 26 rocks thevanes 12 and 13 outwardly away from each other and across the inlet 8.

In accordance with the present invention the fluid motor is renderedoperative to actuate vanes 12 and 13 to a regulating position only whena condition exists which will produce surging. To this end, a loopcircuit is provided having conduits 39 and 40 connected to the ends ofthe cylinder 31 at opposite sides of the piston 32 and a conduit 41connecting conduits 39 and 40 to each other. The conduits 39 and 41 alsoincludes the lower end of cylinder 42 of a piston valve 43 as will beobserved by reference to FIGURE 2. The cylinder 42 has seats 44 and 45at opposite sides of piston valve 43 at the upper and lower endsthereof. Fluid pressure is supplied through a conduit 46 and cylinder 42of piston valve 43 onto the top of the motor piston 32 of the fluidmotor 30 when the piston valve 43 is in its lowermost position engagingthe seat 45; and the flow of motive fluid to the fluid motor is shut offwhen the piston valve is moved to its raised position to engage the seat44. The motive fluid for operating the fluid motor 30 may be suppliedfrom any source, but preferably the conduit 46 is connected to theoutlet 9 from the machine to subject the motor to the pressure of thepumped medium.

The movement of the motor piston 32 is controlled by throttling valvesfor controlling movement in either direction. To this end, an adjustableneedle valve 47 is provided in an extension 40a of the conduit 40 beyondthe connecting conduit 41 which limits the rate of flow of fluid intoand out of the end of the cylinder below the piston 32 as viewed inFIGURE 3. Another adjustable bleed valve 48 is connected to the conduit39 to bleed motive fluid from the line above the piston 32.

Piston valve 43 is yieldingly held in its lowermost open positionillustrated in FIGURE 3 by a spring 49 and is moved to its closed shutoff position by a solenoid 50 acting on the valve stem 43a. Solenoid 50is energized by a switch 51 which is opened by a force resulting from anoperating condition of the compressor 6 at which surging is apt tooccur. In the embodiment illustrated in FIGURE 1 the switch 51 isactuated to open position by a spring 52 and operated to closed positionby a current responsive relay coil 53 in the power line P-3. Thus,during stable operating conditions of compressor 6 with a constant load,the switch 51 is held closed by the current responsive relay coil 53against the action of the spring 52. With switch 51 closed the relaycoil 50 is energized from any suitable source of electric current,illustrated diagrammatically at 54 in FIGURE 1, which actuates thepiston valve 43 into engagement with the seat 44 to shut ofi the supplyof motive fluid to the motor 30 as shown in FIGURE 2. However, when theload falls off to a value at which surging might occur the spring 52opens the switch 51. Upon opening of the switch 51, solenoid 50 releasesthe piston valve 43 which is moved to open position by a spring 49, asshown in FIGURE 3, to bring the anti-surging device 7 into operation.Anti-surging device 7 then controls flow of the medium being pumped toprevent surging.

While a variable current relay coil 53 in the power line P-3 to themotor is illustrated in FIGURE 1 as the control factor for starting andstopping operation of the antisurging device to regulate flow, it willbe understood that any other control factor correlated to a surgingcondition may be used to close or open switch 51. For example, a timermay be used to operate the switch 51 where demand on the blower can beaccurately predetermined, or an element which senses the rate of flow ofthe medium being pumped, or an element that senses the pressure at theoutlet from the blower can be used in place of the current relay coil 53to close or open the switch. While these several control factors, only,are described, it will be understood that any other factor which changesin response to a condition at which surging occurs can also be used. Anapparatus incorporating the anti-surging device of the present inventionhaving now been described in detail, the mode of operation is nextexplained.

When the compressor 6 is operating at a rate above its minimum capacityand is delivering medium being compressed at a substantially constantrate, the operation of the machine is stable and surging will not occur.Under these operating conditions the compressor is doing work on themedium being pumped and the current supplied to driving motor 10 issufficient to maintain switch 51 closed, see FIGURE 1, the solenoid 50energized and the piston valve 43 closed. The medium being pumpedflowing through the inlet 8 acts on the flaps 12 and 13 of theanti-surging control device 7 to collapse them to the folded back toback relationship at the center of the inlet 8 where they present aminimum and negli gible resistance to flow.

However, when the volume of compressed fluid from the compressor 6decreases to some minimum rate with a corresponding increase in pressurein the outlet 9, surging or pulsing between the inlet and outlet is aptto occur. The decrease in the work being done also decreases the currentsupplied to the driving motor 10. This decrease in current flow throughthe current responsive relay 53 then releases the switch 51 which isactuated to open position by the spring 52, see FIGURE 1. Opening of theswitch 51 deenergizes the solenoid 50 so that spring 49 moves the pistonvalve 43 from the position illustrated in FIGURE 2 to that illustratedin FIGURE 3. High pressure fluid from the outlet 9 of the compressor 6then flows through the line 46 and cylinder housing 42 of piston valve43, then through conduit 39 into the cylinder 31 of the fluid motor 30at the top of the piston 32. The high pressure fluid acting on thepiston 32 moved it from the position illustrated in FIGURE 2 to thatillustrated in FIGURE 3. The downward movement of the piston isinitially throttled by the needle valve 47 to prevent oscillation orhunting by the piston.

Downward movement of the piston 32 of the motor 30 is opposed by theforce applied to the vanes 12 and 13 by the medium to be compressed asit flows through the inlet 8 of the machine. Piston 32 operates throughthe piston rod 33, cross-head 34, links 37 and 38 and arms 25 and 26 torock the vanes 12 and 13 from the collapsed back to back relationillustrated in FIGURE 2 to an out wardly extended relation tending toclose the inlet 8. However, as the vanes move outwardly they present agreater surface area to the impact of the medium being pumped as well asto the difference in pressure at opposite sides of the vanes whichopposes their outward movement by the fluid motor 30. Thus, the forceopposing extension of the vanes 12 and 13 increases as the loadincreases, and when the force applied to the piston 32 by the fluid fromthe outlet 9 from the compressor equals the force applied on the vanesby the flow of media through the inlet 8, an equilibrium condition isproduced at which the vanes 12 and 13 will be positioned to producestable flow through the centrifugal compressor 6. With such stable flowno surging will occur. At any time a change in the rate of flow throughthe inlet 8 occurs the vanes 12 and 13 will move to a new position ofequilibrium to maintain stable flow through the machine. Such operationof the centrifugal compressor 6 as controlled by the anti-surging device7 will continue in the unstable range where surging is normally apt tooccur with the vanes 12 and 13 continually adjusting to varying pressureconditions to maintain stable flow.

However, when the flow from the machine 6 increases to a point where anydanger of surging is eliminated with a corresponding increase in theload on the compressor, the current flow through the current responsiverelay coil 53 increases and closes switch 51 to energize solenoid 50.Energization of the solenoid 50 actuates the piston valve 43 from theposition illustrated in FIGURE 3 against the action of the spring 49 tothe position shown in FIGURE 2 to shut off the supply of motive fluid tothe motor 30. The medium being pumped then acts on the vanes 12 and 13to rock them back to the collapsed back to back relationship illustratedin FIGURE 2. Such movement of vanes 12 and 13 is transmitted through thearms 25, 26, links 37, 38, crosshead 34 and piston rod 33 to move thepiston. During such movement of the piston 32 the motive fluid at theupper side thereof flows through the closed circuit including theconduit 39, cylinder 42 of the piston valve 43 and conduits 41 and 40 tothe opposite side of the piston to balance the pressure at oppositesides thereof. The compressor 6 will continue. to operate so long asstable flow through the compressor exists, but when the load againdecreases sufliciently to cause the relay coil 53 to release the switch51, corresponding to a surging condition, the anti-surging device 7 willagain be brought back into operation to actuate the vanes 12 and 13 fromtheir collapsed back to back relation where they produce a negligibleresistance to flow to an extended relation to positively resist flow andproduce stable operation.

FIGURE 5 illustrates the anti-surging control device 7 of the presentinvention applied to a centrifugal machine when operating as anexhauster. In this case the control device is applied to the outlet 9from the machine 6 and its position is reversed so that the vanes moveupwardly to a collapsed position and downwardly to an extended position.The valving system is also reversed so as to connect the head end of themotor fluid cylinder 31 to suction pressure in the inlet 8 and operatethe vanes 12 and 13 to extended positions to throttle flow. Also,instead of controlling the operation of the anti-surging control deviceby a current responsive relay coil 53 as shown in FIG- URE 1, the devicemay be controlled by a deflecting vane 60 responsive to flow in inlet 8to start and stop operation of the device. The pivoted vane 60 ismounted to rock on a shaft 61 and has an eccentric weight 62 projectingfrom one side of its pivotal axis. Vane 60 in the dotted line positionconnects the lines L-1 and L-2 of an electric circuit for energizing thesolenoid 50 and opens the circuit in all other positions. Thus, when themedium being pumped is flowing through the inlet 8 at a rate to producea stable operating condition the vane 60 is swung to close the circuitbetween the lines L-1 and L2, energize the solenoid 50 and actuate thepiston valve 43 as previously explained. However, when the rate of flowis insuflicient to maintain the vane in its circuit closing position, atwhich time a surging condition exists, the eccentric weight rocks thevane to a circuit opening position shown in full lines in FIGURE 5 todeenergize the solenoid 50. The antisurging device is then brought intoaction in the manner previously explained to control flow through theoutlet and thereby maintain stable operating conditions to preventsurging.

It will now ben observed that the present invention provides ananti-surging control device for centrifugal machines which produces anegligible resistance to flow for stable operating conditions and variesthe resistance to flow during unstable operating conditions at whichsurging is apt to occur. It will also be observed that the presentinvention provides an anti-surging control device which is automaticallybrought into and out of operation in response to operative conditions.It will also be ob served that the present invention provides ananti-surging control device adapted for use with a centrifugal machinewhether used as a compressor or an exhauster. It will still further beobserved that the anti-surging device of the present invention is ofrelatively simple and compact construction, economical to manufactureand one which is reliable in operation to perform its intended function.

While several embodiments of the invention are herein illustrated anddescribed it will be understood that further changes may be made in theconstruction and arrangement of elements without departing from thespirit or scope of the present invention. Therefore, without limitationin this respect, the invention is defined by the following claims.

I claim:

1. An anti-surging control for a centrifugal fluid handling machine suchas a compressor and an exhauster which has an inlet and an outletpassage comprising a butterfly valve in one of the inlet and outletpassages, said valve having separate vanes hingedly mounted for rockingmovement on a common axis, the flow of fluid acting on the vanes of saidvalve tending to move them to a collapsed back to back relationship inthe passage in which they are located to produce only a minimumresistance to flow, a fluid motor connected to operate said vanes of thevalve away from each other to extended relation to throttle flow throughthe pass-age, a. source of fluid under pressure, conduit meansconnecting said source of fluid to said motor, a valve in the connectionbetween said source of fluid and said motor, and means operableresponsive to a condition at which surging is apt to occur for openingthe valve to deliver fluid under pressure to said motor.

2. An anti-surging control for a centrifugal fluid handling machine inaccordance with claim 1 in which the fluid motor is a cylinder having areciprocating piston therein, and said valve in the connection betweensaid source of fluid and the motor supplying fluid to one side of saidpiston when open.

3. An anti-surging control for a centrifugal fluid handling machine inaccordance with claim 2 in which an adjustable bleed valve is providedin the connection between the source of fluid and the motor to adjustthe fluid force exerted on the fluid motor.

4. An anti-surging control for a centrifugal fluid handling machine inaccordance with claim 2 in which an exhaust line is provided from thecylinder at the side of the piston opposite the one to which pressurefluid is supplied, and an adjustable valve in said exhaust connection tocontrol the rate of movement of the piston and dampen oscillations.

5. An anti-surging control for a centrifugal fluid handling machine inaccordance with claim 2 in which a loop circuit connects the ends of thecylinder at opposite sides of the piston, said loop circuit includingsaid valve between said source of fluid and said motor, and said valvein one position connecting the source of fluid under pressure to oneside of the piston and in its other position connecting the oppositeends of the cylinder to each other to allow quick response of the pistonin the fluid motor.

6. An anti-surging control for a centrifugal fluid handling machine inaccordance with claim 1 in which one of the vanes is connected to ashaft extending across the passage in which it is located, the othervane being connected to a sleeve surrounding the shaft, one end of saidshaft and sleeve projecting outwardly from the passage in which thebutterfly valve is located, arm-s projecting radially from theprojecting ends of the shaft and sleeve, respectively, to the oppositeside of the shaft from its vane, a reciprocating crosshead operated bythe fluid motor, and 'links connecting the crosshead to the outer endsof the extended arms.

7. An anti-surging control for a centrifugal fluid handling machine inaccordance with claim 1 in which the machine is driven by an electricmotor, a power line for the driving motor, the means operable responsiveto a condition which produces surging is a solenoid for actuating thevalve, an electric circuit for the solenoid comprising an electricswitch biased to one position, and a magnetic winding in the power lineresponsive to the current flow therein for actuating the switch to itsother position.

8. An anti-surging control for a centrifugal fluid handling machine inaccordance with claim 1 in which the means responsive to a condition atwhich surging is apt to occur comprises a vane pivotally mounted in oneof the passages to and from the machine, an eccentric weight normallybiasing the vane toward one position, the flow of fluid through saidport acting on the vane against the action of the weight to bias theswitch to its other position, and an electric circuit for actuating saidvalve and controlled by said switch.

9. An anti-surging control for a centrifugal fluid handling machine inaccordance with claim 1 which operates as a blower, said butterfly valvebeing located in the inlet passage to control the flow therethrough, andsaid source of fluid under pressure being fluid from the outlet passagefrom the compressor.

10. An anti-surging control for a centrifugal fluid handling machine inaccordance with claim 1 which operates as an exhauster, said butterflyvalve being located in the outlet passage, the source of pressure beingthe pressure produced in the inlet passage and connected to the cylinderof the fluid motor.

References Cited UNITED STATES PATENTS Fleck 251212 Hinz 230-115Schellens 230-115 Haugsted 2301l5 Hafer 230-22 Kusarna 230115 ROBERT M.WALKER, Primary Examiner.

LAURENCE V. EFNER, Examiner.

1. AN ANTI-SURGING CONTROL FOR A CENTRIFUGAL FLUID HANDLING MACHINE SUCHAS A COMPRESSOR AND AN EXHAUSTER WHICH HAS AN INLET AND AN OUTLETPASSAGE COMPRISING A BUTTERFLY VALVE IN ONE OF THE INLET AND OUTLETPASSAGES, SAID VALVE HAVING SEPARATE VANES HINGEDLY MOUNTED FOR ROCKINGMOVEMENT ON A COMMON AXIS, THE FLOW OF FLUID ACTING ON THE VANES OF SAIDVALVE TENDING TO MOVE THEM TO A COLLAPSED BACK TO BACK RELATIONSHIP INTHE PASSAGE IN WHICH THEY ARE LOCATED TO PRODUCE ONLY A MINIMUMRESISTANCE TO FLOW, A FLUID MOTOR CONNECTED TO OPERATE SAID VANES OF THEVALVE AWAY FROM EACH OTHER TO EXTENDED RELATION TO THROTTLE FLOW THROUGHTHE PASSAGE, A SOURCE OF FLUID UNDER PRESSURE, CONDUIT MEANS CONNECTINGSAID SOURCE OF FLUID TO SAID MOTOR, A VALVE IN THE CONNECTION BETWEENSAID SOURCE OF FLUID AND SAID MOTOR, AND MEANS OPERABLE RESPONSIVE TO ACONDITION AT WHICH SURGING IS APT TO OCCUR FOR OPENING THE VALVE TODELIVER FLUID UNDER PRESSURE TO SAID MOTOR.